The present invention relates to a septic system for the decomposition of sewage and, more particularly, to such a system which is especially adapted for use with more than one drain field for ground seepage of effluent.
Septic systems are extensively used to treat sewage from individual residences and the like in areas not served by sewers. Such a system includes, in general, a septic tank into which the sewage to be treated is fed. Because of their different densities, the solid and liquid components of the sewage separate within the tank. The solid material is then decomposed within the tank by the action of anaerobic bacteria. The liquid is conveyed out of the tank and distributed through an area of subterranean soil, commonly referred to as a drain field, through which it percolates and becomes purified before again joining the underground water table.
Before a septic system can be effectively used in an area, the soil conditions must be such that adequate percolation of the liquid effluent from the tank is posible. Even when the sewage system is located in an area of optimum soil conditions, it is not unusual for the drain field soil to become saturated after a long period of use, e.g., ten years. When a drain field does become so saturated, it has been necessary to modify the septic system by providng a new drain field. It will be recognized that because of the required excavation and installation of new pipes, the provision of such a new drain field is relatively expensive. Moreover, the necessity for a new drain field is often not discovered in time to prevent unpurified liquid from joining a water table. Because of such, it is not uncommon for there to be contaminated wells and other sources of water supply in areas in which sewage is treated by spetic tanks.
It has recently been found that the life of a septic tank drain field can be considerably extended if it is periodically allowed to dry out. For this reason, it has been proposed that more than one drain field be initially provided, and that the effluent from the septic tank be periodically diverted from one of such drain fields to another so that such fields will alternately be allowed to dry out. The resulting capability of enabling drain fields periodically to dry out extends the life of a septic system considerably beyond that expected for a similar system having the same number of drain fields, to which effluent is continuously directed.
While there are diversion systems now available for selectively directing the effluent from a septic tank to a chosen one of a plurality of drain fields, they suffer from several deficiencies. For one, they generally include relatively complex and expensive valve arrangements. Moreover, some available do not provide a ready indication of which drain field or fields are in use, and which are not. Because it is only necessary to switch drain fields about once a year, it will be recognized that no provision for indicating which drain field or fields are receiving effluent and which are not, can result in confusion.